3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
The 3GPP LTE-A employs various techniques such as carrier aggregation, relay, etc. The 3GPP LTE system is a single carrier system supporting only one bandwidth (i.e., one component carrier) among {1.4, 3, 5, 10, 15, 20} MHz. On the other hand, the LTE-A employs multiple carriers using carrier aggregation. The carrier is defined with a center frequency and a bandwidth. A multiple-carrier system uses a plurality of component carriers having a narrower bandwidth than a full bandwidth.
A user equipment (UE) persistently performs measurement to maintain quality of a radio link with a serving cell from which the UE receives a service. A cell or frequency to be measured is referred to as a measurement object, and is associated with a reporting configuration for independently triggering reporting of a measurement result for each measurement object. The UE performs measurement on the measurement objects, and when the reporting configuration is satisfied, reports the measurement result to a base station (BS).
In the conventional measurement configuration structure, the reporting configuration can be associated with only one measurement object.
When measurement objects and reporting configurations are associated with each other in a one-to-one manner, the UE reports a measurement result individually to each measurement object, and if the number of measurement objects increases, the number of times of transmitting a measurement report message by the UE also increases. If the reporting configuration includes an inappropriate configuration value, measurement reporting of the UE may be excessively frequently triggered or, on the contrary, reporting of the measurement result may be significantly delayed.
When reporting configurations are independently associated with respective component carriers in a multiple carrier system, an overload for reporting a measurement result may increase as the number of component carriers increases.
In addition, according to capability of the UE or a cell environment, the UE does not have to use all of the plurality of component carriers.
Accordingly, there is a need for a method capable of more effectively reporting a measurement result on a plurality of component carriers in a wireless communication system.